SEARCH FOR DOUBLY-CHARGED NEGATIVE-IONS OF SMALL CARBON CLUSTERS

A search has been conducted for dianions of small carbon clusters C-n( 2-)(2 less than or equal to n less than or equal to 8) formed by laser ablation of graphite. A multicoincidence time-of-flight technique has been used to monitor fragment ion-pairs produced in dianion decay. No evidence is found for C-2(2-) dianions. However, detection of anion-p airs C-n(-)-C-n(-) (n > 1) provides evidence for higher-n (n > 2) clus ter dianions which exhibit a preference for symmetrical decay. Ab init io computations of potential energy curves have been carried out for C -2(2-) dianion states; results indicate too short a lifetime against a utodetachment for detection in our experiments. (C) 1997 Elsevier Scie nce B.V.